Laura Osete-Cortina

Electrochemical identification of metal ions in archaeological ceramic glazes by stripping voltammetry at graphite/polyester composite electrodes

The electrochemical response of metal ions in different samples of coloured ceramic tin-lead glazes attached to graphite/polyester composite electrodes is described. In addition to the ubiquous signals for lead, reductive dissolution processes are followed by anodic stripping peaks for Co, Cu, Sb, Mn, Sn and Fe, enabling the direct identification of such elements in microsamples proceeding from archaeological glazed tiles from Valencia (Spain) workshops (16th-18th century). Additional anodic and cathodic peaks corresponding to redox processes involving metal species in solution generated during stripping processes are also used. Peak potentials, Tafel plots and shape parameters are used for characterising the different species.

Identification of Manganese(IV) Centers in Archaeological Glass Using Microsample Coatings Attached to PolymerFilm Electrodes

Identification of MnO2 nodulae in archaeological glass by linear scan and differential pulse voltammetry using abrasive-conditioned microsamples attached to polymer film (Elvacite 2044) electrodes is described. Voltammetric responses for manganese-containing samples parallels to those obtained for β- and γ-MnO2 upon immersion of modified electrodes into NaCl, KCl and acetic/acetate aqueous media. The observed electrochemical response provides information on the open microporous structure of the MnO2 forms and the conditions of their formation during the weathering process of buried glass.

Study of behaviour on simulated daylight ageing of artists’ acrylic and poly(vinyl acetate) paint films

AbstractThis work proposes a multi-method approach that combines advanced microscopy (SEM/EDX, AFM) and spectroscopy (UV-vis and FTIR) techniques. This approach not only characterises the behaviour of the additives of two commercial poly(vinyl acetate) (PVAc) and acrylic emulsion paints but also simultaneously characterises the changes in chemical composition and morphology observed in the paint films as a result of ageing due to the paints being exposed to an intense source of simulated daylight. In parallel, a series of mechanical tests were performed that correlate the chemical changes in composition and the changes observed in the films’ mechanical properties. This work was a comparative study between both types of acrylic and PVAc paints. The results obtained are of great interest for the modern paint conservation field as they provide valuable information on the mid- and long-term behaviours of these synthetic paints. FigureTensile test of phthalocianyne blue Liquitex® paint film

On the dehydroindigo contribution to Maya Blue

A series of data from voltammetric, spectral, and UPLC–MS and Py–GC–MS analyses of extracts from synthetic Maya Blue-type specimens provides evidence on the presence of a significant amount of dehydroindigo, identified on the basis of its MS, FTIR, and UV–Vis signatures, accompanying indigo and other minority compounds, supporting the view of this material as a complex polyfunctional organic–inorganic hybrid material. Estimates of dehydroindigo/indigo in-depth distribution and thermochemical data for the dye association to the clay from chromatographic and voltammetric data are provided.

Study of ageing of ketone resins used as picture varnishes by FTIR spectroscopy, UV-Vis spectrophotometry, atomic force microscopy and scanning electron microscopy X-ray microanalysis.

This paper presents a study of thin films of the commercial ketone resins Laropal K80, Keton N and MS2A, attempting to reproduce the pictorial layers and protective finishes commonly present in contemporary paintings. Chemical and morphological changes due to the degradation effect of environmental agents have been specially considered. For this purpose, three different accelerated ageing processes were applied to a series of specimens prepared from the studied commercial products: thermal, UV light and ageing in an SO2-polluted chamber. Spectroscopic techniques such as FTIR spectroscopy and UV–Vis spectrophotometry were applied in combination with microscopic examination techniques, namely, AFM and scanning electron microscopy energy dispersive X-ray microanalysis (SEM-EDX). Chemical changes due to UV light and thermal ageing are in good agreement with those previously reported in the literature. Bleaching exhibited by the three commercial products after exposure to a SO2-saturated atmosphere has been related to the diffusion of SO2-rich water vapour into the film. This effect was particularly strong in the MS2A resin due to the higher content of hydroxyl groups in this product.

‘Maya chemistry’ of organic–inorganic hybrid materials: isomerization, cyclicization and redox tuning of organic dyes attached to porous silicates

Association of indigo and lapachol dyes to aluminosilicate clays yields polyfunctional organic–inorganic hybrid materials forming Maya Blue-like systems. Upon partial removing of clays zeolitic water by moderate thermal treatment, abundant isomerization, cyclicization and oxidation reactions occur defining a ‘Maya chemistry’ whose complexity could explain the versatile use of such materials in the pre-Columbian cultures and permits the preparation of polyfunctional materials potentially usable for therapeutic and catalytic purposes.

Voltammetric analysis of Pinus needles with physiological, phylogenetic, and forensic applications

AbstractPolyphenolic compounds are electrochemically active components of vegetal matter which were targeted under simple experimental conditions to produce voltammetric profiles characterizing the metabolite composition. Application to bivariate and multivariate chemometric techniques permits to discriminate the species and age of plant leaves, illustrated here for the case of six Pinus species from two different subgenera. Such responses, associated with the electrochemical oxidation of polyphenolic compounds (quercetin, gallic acid, ellagic acid, among others), define a voltammetric profile which varies systematically with the age of the leaves for the different species. The application of this methodology for phylogenetic studies, plant physiology, forensic science, and chemoecology is discussed. Graphical AbstractImage of Pinus in a typical Mediterranean forest; Courtesy of the Botanic Garden of the University of Valencia

Multimethod analysis of Iranian Ilkhanate ceramics from the Takht-e Soleyman palace

AbstractThe present work describes an analytical study performed on several pieces of Iranian Ilkhanate glazed ceramics from the Takht-e Soleyman palace (Iran, thirteenth century). Several advanced instrumental techniques, including pyrolysis–gas chromatography–mass spectrometry, Fourier transform IR spectroscopy, light microscopy, X-ray diffraction, scanning electron microscopy–X-ray microanalysis and voltammetry of microparticles, were used. The results obtained led to identification of the chemical and mineralogical composition of the pastes and glazes and the colouring agents. Corrosion processes associated with the extreme burial conditions in which the pieces remained for centuries were characterized in some areas of the glazes. A drying oil was identified as the main component of the organic material that was used as the adhesive for the decorative gold sheets applied on the glazes. This finding is in good agreement with traditional recipes. Interestingly, this drying oil exhibits an unusual composition as the gold sheet preserved it from external ageing agents (light, atmosphere, etc.). FigureTiles with cobalt blue glaze from the indoor decoration of the Takht-e Soleyman Palace (13th-15th centuries, Iran). a: 20986-8, b: 20986-10 and c:21300a

Potential Application of Voltammetry of Microparticles for Dating Porcine Blood-based Binding Media used in Taiwanese Architectural Polychromies

A method for dating Hemoglobine-containing archaeological samples using the voltammetry of microparticles is described. This is based on the record of the voltammetric response of such materials attached to paraffin-impregnated graphite electrodes in contact with aqueous acetate buffer. Signals attributable to the Fe(III)/Fe(II) iron couple and their catalytic enhancement in the presence of H(2)O(2) can be correlated, via first-order reaction kinetics, with the time of aging of the samples. The method has been applied to the study and dating of the polychromed architectural decoration of different parts of the architectural complex of the Longshan Temple in Lukang (18(th)  century, Taiwan).

Analytical Study of a Resinous Material Used as Sealing in Ancient Pottery Found in an Archaeological Site by Thermally Assisted Hydrolysis Methylation–Gas Chromatography–Mass Spectrometry, Vibrational Spectroscopy and Light Microscopy

Abstract A resin sample was found in the archaeological site of Lixus (Morocco), belonging to the second century BC. The resinous material was found inside an amphora containing iron remains used in the plug as sealing material to hermetically close the pottery. The resinous sample was studied by several analytical techniques, as thermally assisted hydrolysis and methylation–gas chromatography–mass spectrometry (THM–GC–MS), Fourier transformed infrared spectroscopy (FTIR), and light microscopy. The material was identified as a Pinaceae resin. Therefore, a modern pine resin was also analyzed to consider the influence of aging in the archaeological sample. The ancient material was found not too oxidized, owing to the conservation conditions inside the amphora, protected from air and moisture.